Present designs of mechanical sleeping systems typically include a combination of upper mattress and lower base. The mattress is usually thick foam or a system of inner springs. The aim of the mattress is to provide micro adaptability to the contour of the human body. The lower base supporting the mattress is typically a platform using transverse slats which act as simply supported beams.
The purpose of the mattress base is to provide for macro adaptability of the body not taken care by the mattress, as well as to elevate the mattress from the ground and to provide aeration of the mattress. The combined performance of the mattress and the base results in the largest mattress flexing/compression at the heaviest portion of the human body such as the hips and the shoulders. This leaves the lighter, concave portions of the body less supported. The most dramatic consequence of this arrangement is at the transition between the shoulders and the head, where the neck is essentially unsupported. This situation is remedied to some degree by using pillows of various shapes and firmness and by varying spring characteristics in the mattress or in the base slats, at the anticipated locations of improper body support. However, this approach fails whenever a person changes or modifies the sleeping position since a completely different body contour is associated with each body position while the body weight distribution stays the same. In addition, there is a large variation of body contour and weight distribution, even when the predominant side sleeping position is adopted, which could not be accommodated by the average spring properties of a mattress or a base.
Mechanical systems that self-adjust to the body contour rather than passively reacts to the body weight distribution are known. However, these systems are characterized by a limited capacity to compensate for the variation of the human body contour. CH 684779 discloses a system with interactive adjacent slats. When a slat is pushed downward it forces the adjacent slats upward by connecting the slats with a common belt or cord. U.S. Pat. No. 6,647,574 describes the interaction between adjacent areas of bed base surface in 3-D by employing wave springs. WO83/01563 describes the use of slats that are not attached at the ends to the frame and that interact with each other using a rope-sheath system comprising dynamic and stationary rope sheaths mounted between the slats and connected by a rope. U.S. Pat. No. 5,924,149 describes attachment of the ends of the slats to an elastomeric bridge suspension mounted to base frame.
Alternate systems are based on two pulley systems, each pulley system comprising a series of pulleys connected with a common cord and employing a guide rod that connects a pulley to the slat. These systems increase the capacity to compensate for the variation of the human body contour. For example U.S. Pat. No. 3,717,376 discloses a chair having two pulley systems, each pulley system is attached to the side-frame of the chair and comprises a series of pulleys. Each pulley is attached to one end of a rod that is guided within a bracket. The other end of the rod is attached to a slat that is free at each end so that the entire slat may move up or down. WO85/02987 describes the use of a two pulley system, each pulley system comprising rods guided in slides, and the rods are pivotally attached to slats. Each slat is free at the ends so that the entire slat may move up or down during use. CH 663339 describes a bed having two pulley systems, with each pulley system located within the sides of the bed frame. Each side of the bed frame comprises a series of slots, each slot guiding the vertical movement of a dynamic pulley. The ends of each of the slates are connected to the dynamic pulleys, and the slats rise and lower with movement of the dynamic pulleys. A similar arrangement is provided in U.S. Pat. No. 5,058,224 where the rods are guided in slots and cylinders located in the sides of the bed frame, and slats are pivotally attached to the dynamic pulleys. Patent AT 401606 describes slides for vertical guiding the rods. Each rod is pivotally attached to a slat, and each slat is free at each end. In several of the systems described above, both pulley systems need to rise and lower together in order to prevent the slats from jamming between the sides of the bed frame.
DE 19818172 describes the uses of movable plates (in place of rods) that run the width of the bed and that are attached to slats on their upper surface. Each plate comprises a linear bearing that is centrally located and interlaced with a cord to provide vertical guided movement of the slats. In U.S. Pat. No. 7,512,999 B2 a pulley system having vertical sliding pistons attached to dynamic pulleys at one end, and slats at the other, is shown. Each piston stem is surrounded by a spring. The slats may be slidably fixed to the bed frame at their ends.
Common to all of above inventions is the use of slats that are self-adjustable by mechanisms attached to the ends, or near the ends, of the slats and to the two opposing sides of the base frame. The arrangement of tandem mechanisms not only leads to an expensive solution, but is also difficult to use because of problems with mutual interference of the mechanism components, increased maintenance problems, movement noise, and an inconvenient design arrangement at the edge of the bed. It has proved difficult to design a bed having a thin mattress with a large range of movement at the edge of the base without interference with the bed frame. These systems still rely on the mattress to varying degrees to compensate for the human body weight and shape variation.